Field of the Invention
The invention relates to a method for controlling an internal combustion engine, in particular, an internal combustion engine with quantity control, that is to say, an internal combustion engine operating on the Otto principle.
In a prior art method for controlling an internal combustion engine disclosed in German Published, Non-Prosecuted Patent Application DE 38 39 611 A1, the air ratio is determined individually for each cylinder by a lambda probe. As a function of the air ratio determined for the respective cylinder, a correction signal for correcting the activation of a fuel injection valve is determined, specifically with the effect of an approximation of all the air ratios in the respective cylinders of the internal combustion engine to the value xcex=1.
Alternatively thereto, German Published, Non-Prosecuted Patent Application DE 38 39 611 A1 discloses, a determination of a correction signal for activating an actuator of a throttle member of the internal combustion engine as a function of the respective individual-cylinder air ratio.
The disadvantage of both alternatives of the prior art methods, however, is that, although the air/fuel ratios in the individual cylinders are approximated to one another, the torques generated in the individual cylinders may vary, and the variation is detected by a driver of a vehicle in which the internal combustion engine is disposed as an unevenly running internal combustion engine or as jolting.
In a further prior art method disclosed in International publication WO 90/07051, corresponding to U.S. Pat. No. 4,936,277 to Deutsch, the torque contributions of the individual cylinders of the internal combustion engine are assimilated to one another by a monitoring of the power output by the respective cylinders and individual-cylinder correction of the fuel mass as a function of the respective power in the cylinder. Although, by such a method, an assimilation of the torque contributions of the individual cylinders is achieved, the method may lead to deviations in the air ratio in individual cylinders from a predetermined desired value for the air ratio, these deviations being capable of causing damage to a three-way catalytic converter disposed in an exhaust tract of the internal combustion engine.
It is accordingly an object of the invention to provide a method for controlling an internal combustion engine that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that ensures low-emission and at the same time comfortable control of an internal combustion engine.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for controlling an internal combustion engine having cylinders each with at least one fuel injection valve and at least one actuator setting a mass of air supplied to the cylinder, including the steps of detecting an air/fuel ratio in a cylinder and individually determining an air/fuel variable for each cylinder, detecting a torque generated in a cylinder and individually determining a torque variable for each cylinder, individually correcting an activation of the fuel injection valve for each cylinder as a function of a detected quantity of the air/fuel variable for each cylinder and a desired value of the air/fuel variable, and individually correcting an activation of the air mass-setting actuator for each cylinder as a function of a detected value of the torque variable to effect an assimilation of the torques generated by the individual cylinders.
With the objects of the invention in view, there is also provided a method for controlling an internal combustion engine having cylinders each with at least one fuel injection valve and at least one actuator setting a mass of air supplied to the cylinder, including the steps of detecting an air/fuel ratio in a cylinder and individually determining an air/fuel variable for each cylinder, detecting a torque difference variable representing differences between torques generated in the cylinders and individually determining the torque difference variable for each cylinder, individually correcting an activation of the fuel injection valve for each cylinder as a function of a detected quantity of the air/fuel variable for each cylinder and a desired value of the air/fuel variable, and individually correcting an activation of the air mass-setting actuator for each cylinder as a function of a detected value of the torque difference variable to effect an assimilation of the torques generated by the individual cylinders.
In accordance with another mode of the invention, the torque variable is the torque.
In accordance with a further mode of the invention, the cylinder has a combustion space and the torque variable is a combustion space pressure.
In accordance with an added mode of the invention, the air/fuel ratio is detected with at least one sensor.
In accordance with an additional mode of the invention, the torque is detected with at least one sensor.
In accordance with yet another mode of the invention, the torque difference is detected with at least one sensor.
In accordance with yet a further mode of the invention, the air mass-setting actuator is a gas exchange valve.
In accordance with yet an added mode of the invention, an air/fuel ratio is detected in all of the cylinders and an air/fuel variable is individually determined for each cylinder.
In accordance with yet an additional mode of the invention, a torque generated is detected in all of the cylinders and a torque variable is individually determined for each cylinder.
In accordance with again another mode of the invention, a torque difference variable representing differences between torques generated in all of the cylinders is detected and the torque difference variable is individually determined for each cylinder.
In accordance with again a further mode of the invention, the engine has a crankshaft connected to the cylinders, and the torque difference variable is derived from a rotational speed of the crankshaft.
In accordance with a concomitant mode of the invention, the torque difference variable is derived from a measurement signal of a combustion space pressure sensor.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for controlling an internal combustion engine, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.